Various techniques have been developed to transfer energy wirelessly, and in some cases over long distances. Examples of such systems include U.S. Pat. Nos. 6,327,504; 6,772,011; 7,825,543; and 8,076,801 and U.S. Pub. Nos. 2010/0102639 and 2010/010909445, the entire contents of which are incorporated herein for all purposes by reference.
More recently, there has been development into powering an implanted device wirelessly with a Transcutaneous Energy Transfer (TET) system. Many implantable medical devices require power sources or electrical systems to power the implant. Typically this is achieved using transcutaneous wiring to connect a power source to the implant. TET systems are designed to replace or supplement the transcutaneous wires.
TET systems typically include a lot of hardware and components. One example of a TET system includes the transmission of energy from a transmit coil to a receive coil using an oscillating magnetic field. The TET system also includes a power supply (e.g., battery and/or power conditioner to connect to AC mains) and processing electronics (e.g., solid state electronics and a controller), and other components. It can be burdensome for a patient to carry all these components, in particular for life-saving devices which must be carried at all times. Furthermore, TET systems often require precise alignment of components. Accordingly, there is a need for improvements to peripherals for carrying the necessary system components.
There is also the need for improved utilization and positioning of TET components. Modern medical devices typically require maximal power efficiency. For example, pumps such as ventricular assist devices (VAD) require a relatively high level of sustained and continuous power. With the advances of medical technology, there are an increasing number of implanted medical devices which can benefit from improvements in wireless energy transmission. Improvements in power usage can translate to meaningful reductions in the form factor of the internal power storage (e.g., battery). Improvements in power transmission can also lead to improvements in operation. For example, a slight improvement in power efficiency can mean significant increases in run time on the battery thus improving patient quality of life (QoL).
TET systems by their nature are sensitive to changes in the system. Even small relative changes to the relative orientation between the transmit and receive coil—distance or angle—can lead to a dramatic increase or decrease in power transmission. Indeed, many modern TET systems can only withstand a separation distance on the order of millimeters and require the coils to be generally in desired alignment. Any deviations can drop the power transmission efficiency below acceptable levels. Some existing TET systems for implantable medical devices require the implanted receiver coil to be positioned just under the skin, and typically include a mechanical feature to maintain exact alignment between the receive and transmit coils. However, by implanting these devices directly under the skin, the size and power requirements of these implanted devices is limited if they are to be powered by a TET system. Moreover, many TET systems are system to changes even within an operational range. For example, if one coil is moving or vibrating rapidly with respect to the other coil the power efficiency will drop dramatically.
The lack of effective positioning systems means that many TET systems are designed for placement of the transmit and receive coils directly adjacent each other in the pectoral region. The pectoral region is known to be relatively stable during activity due to the minimal amount of soft tissue and fat. There is less variability from patient to patient. In part for this reason the pectoral region is a common placement for implantable cardioverter defibrillators (ICD).
Accordingly, there is a need for devices and methods for addressing these and other problems. There is a need for systems and methods that reduce the burden on the patient and improve power transmission. There is the need for improvements to wearable devices for use with wireless energy transfer systems, and in certain respects TET systems.